Hate crimes in Los Angeles County have increased, with almost 500 hate crimes recorded in the county last year, according to a new county report.

The county's Commission on Human Relations tallied 483 reported hate crimes in 2015, nearly 100 more than the previous year. There were 390 reported hate crimes in L.A. County in 2014.

Most offenses were motivated by race or ethnicity. African-Americans were victimized the most; 58 percent of the racially-motivated hate crimes last year involved black victims.

There were also increases in crimes against those who are gay, lesbian and transgender, Jewish, Muslim, Mexican, Chinese, and Armenian, among others. While most incidents involved vandalism, more serious crimes included aggravated assault.

Hate criminals are motivated by several factors, said Robin Toma, executive director of the L.A. County Human Relations Commission. For example, last November's terror attacks in Paris and the December mass shooting San Bernardino led to a spike in anti-Muslim crimes.

Toma and other speakers at a news conference Thursday said harsh rhetoric against Muslims, Latinos and others from GOP presidential candidate Donald Trump's campaign may also have played a part in the increase.

“There is no question that in the current environment, the freedom to express stereotyped views of people, to assign negative things to entire groups, is being encouraged," Toma said.

But some perpetrators are themselves people of color. County officials said 59 percent of the perpetrators in anti-African-American cases were Latino, for example. L.A. County Sheriff's Detective Christopher Keeling said Latino gangs often target African-Americans.

“They don’t want them in the neighborhood," Keeling said. "They are driving by saying, ‘You need to move out’ as they are moving in.”

In turn, African-Americans who feel attacked will retaliate against Latinos, Keeling said.

Gang members were suspected perpetrators in 12 percent of the reported hate crimes, according to the report. Thirteen percent of the crimes involved white supremacist ideology.

The report also concludes that many hate crimes are going unreported, and the crimes cited "likely represent only a fraction" of those committed in 2015.